
<script>
    var res = '1234'.match(/(\d)(\d)(\d)(\d)/);
    console.log(res);
  </script>
  
  <script>
    var str = 'Regular Capture';
    var reg = /(\w+)\s(\w+)/gi;
    var newstr = str.replace(reg, '$2 $1');
    console.log(newstr);    // 输出结果为：Capture Regular
  </script>
  
  <script>
    // ① 非捕获
    var reg = /(?:J)(?:S)/;
    var res = 'JS'.replace(reg,'$2 $1');
    console.log(res);    // 输出结果：$2 $1
  
    // ② 捕获
    var reg = /(J)(S)/;
    var res = 'JS'.replace(reg,'$2 $1');
    console.log(res);    // 输出结果：S J
  </script>
  
  <script>
    var str = '13335 12345 56668';
    var reg = /(\d)\1\1/gi;
    var match = str.match(reg);
    console.log(match);    // 输出结果为：(2) ["333", "666"]
  </script>